The long term objective of this project is to develop chemotherapeutic agents belonging to the antifolate series for the treatment of various forms of human cancers. To achieve this objective, three classes of folate analogues will be synthetized and evaluated for their antitumor activites using several bilogical test systems. These compounds are: 1) analogues of the recently described antileukemic agent, 5,8-dideaza-N10-propargyl folate, which contain a pteridine ring system; 2)compounds possessing a 2-amino -4-hydroxyquinazoline ring system, but otherwise modified at the N10-position with substituents which are very similar to the propargyl group, having slight variations in their steric and electronic environment; 3) analogues of aminopterin, which are substituted at the N10-position which are potential inhibitors of both dihydrofolate reductase and thymidylate synthase. All these compounds will be evaluated for their: a) antifolate activities using folate requiring microorganisms; b) enzyme inhibitory potencies using both bacterial and mammalian dihydrofolate reductase and thymidylate synthase in vitro; c) antitumor activities using L1210, S180 and Ehrlich tumor cells in culture; d) transport influx in L1210, S180 and Ehrlich tumor cells; and e) antitumor activity in mice bearing methotrexate sensitive and methotrexate resistant L1210 leukemia. Those compounds which show promising preliminary activities in the above test systems will be further evaluated for their substrate or inhibitory activities towards dihydrofolate reductase and thymidylate synthase derived from human cell lines (KBP and KB/6b). In addition, they will be tested as inhibitors of the growth of human KBP and KB/6b (high DHFR) cell lines in culture.